This invention relates to a method and apparatus for monitoring refrigerant conditions within a refrigerant circuit and comparing the monitored conditions to desired conditions. More particularly, the present invention discloses a method and apparatus for actuating a signal should the monitored conditions differ from desired conditions.
Modern air conditioning systems are relatively complex and may comprise a number of monitors and controls. These systems have compressors that can operate at various gradations of capacity between zero and 100 percent, depending on the load on the air conditioning system. Thus, if the load on the system is high, the compressor will be operating near full capacity, while if the load is low, the compressor will be at a relatively low capacity. In addition, air conditioning systems are typically in an off state for a large portion of the calendar year. During the winter months, air conditioning systems remain inactive for long periods of time.
Recently, it has become a major concern to prevent leakage of refrigerant, and in particular chlorofluorocarbons such as freon, into the environment. Among the steps taken to address this concern are devices for changing the refrigerant within an air conditioning system in which the refrigerant within the system is captured when changed. These steps are taken to prevent the escape of refrigerant into the environment, since refrigerants may damage the ozone layer. Preventing escape of refrigerant into the environment is thus a problem faced in the air conditioning field.
However, many modern air conditioning systems do not monitor the refrigerant accurately in order to determine whether there may be leakage. In a large air conditioning system, even a relatively small leak can amount in a great deal of refrigerant reaching the environment. Also, the loss of refrigerant affects the efficiency of the air conditioning system resulting in greater power usage.
Some prior art air conditioning systems do monitor a refrigerant condition, typically the pressure, and actuate an alarm should that condition reach a preset alarm level. A leak will normally cause a pressure loss and thus can be identified by monitoring pressure. The prior art may monitor a refrigerant condition such as the pressure at a low-pressure point in the air conditioning system and compare that pressure to a preset alarm level. If the low-pressure is beyond that preset alarm level, a determination is made that there is some problem in the air conditioning system, and an alarm is actuated, often shutting the system down. These types of systems may monitor both high and low-pressure at various points within the air conditioning system.
These prior art systems do not adequately address the problem of refrigerant leakage, instead, they merely compare the actual refrigerant condition to a preset alarm level. The preset alarm level does not vary with varying environmental conditions even though the conditions within the refrigerant circuit of the air conditioning system do vary with varying environmental conditions. Also, these preset alarm levels do not vary for variable operating conditions of the air conditioning systems, such as full or partial capacity of the compressor, or an off condition of the air conditioning system. They do not operate at all when the system is off. The low-pressure expected at a particular point in an air conditioning refrigerant system may be different for a full capacity condition as opposed to a 50 percent capacity condition. Prior art systems that do not vary the alarm levels necessarily set the alarm levels at the lowermost or highermost condition which could reasonably be expected during normal operating conditions of the air conditioning system. Thus, these preset alarm limits cannot accurately monitor the refrigerant circuit and detect a small leak.
It is therefore an object of the present invention to disclose a refrigerant loss prevention system which is sensitive to leakage and actuates an alarm signal when leakage is detected.